1. Field of the Invention
The invention relates to a type of motor rotor system.
2. Description of the Related Art
Conventional brushless DC motors employ a position sensor (Hall element) to measure the position of a rotor so that a motor controller can send a timely phase change command. Now there appears a sine wave control mode with a position sensor. Under such a control mode, a main magnetic field of a motor rotor uses strong magnetism; therefore a driving control signal has a higher consistency requirement for motor counter EMF and Hall output signals. If the consistency is insufficient, an abnormal phenomenon will occur when a program used in one motor is used in another one. In a minor case, motor noise and vibration will be aggravated, efficiency will fall, and unique advantages of a sine-wave motor will be lost. In a serious case, a motor will jitter and lose synchronization. Present rotor systems also have the following problems: 1. if a first-level magnetic inductive ring is added behind a main magnetic field of a motor, the following problems will occur that relative position between the main magnetic field and the inductive magnetic field is not easy to be controlled and measurement accuracy will be affected due to low accuracy; 2. if an enterprise having a relatively good magnetizing process uses the main magnetic field and the inductive magnetic field together for magnetizing, it is not suitable for strong magnetic materials such as sintered NdFeB but low magnetic materials such as ferrite or bonded NdFeB because of limited process; 3. If an adjustable Hall component is mounted behind the rear cover of a motor, operators can drag the counter EMF to measure relative position of Hall signals and counter EMF waveform and then adjust the Hall component to achieve the required relative position relationship between the main magnetic field and the inductive magnetic field. However, disadvantages of this method are obvious including poor processability, low overall accuracy, big differences of motor performance, and unfriendly installation.